The victors have an emotive name for it: seiken kotai, or regime change. It came in brutal fashion on Sunday August 30th when Japan, Asia’s richest democracy, dumped the party that has ruled it for almost all of the last 53 yearsand gave a huge win to one that until recently had little idea of how it would govern.

In a historic result, unofficial results showed that the Democratic Party of Japan (DPJ), a leftist grouping of ruling-party renegades, social democrats and socialists, was heading for a landslide. It is led by Yukio Hatoyama, a mild-mannered career politician likely to be the next prime minister. He promises a government less beholden to the powerful civil service, wants to temper the free market and is keen to dole out cash to the disadvantaged in the economically stagnant and ageing country. He declined to name a cabinet until he is confirmed as prime minister in a special session of the lower house, or Diet. That may be within the next two weeks.

Jubilant cries of Banzai! echoed around the DPJ’s victorious campaign offices. NHK, the public broadcaster, said the party had won 308 seats in the Diet, with almost all the seats counted, as polls had largely predicted. The DPJ hopes to forge a coalition with two minor parties that would give it a two-thirds majority, enabling it to force through legislation. But the three parties do not see eye to eye on all issues, which means plenty of haggling will be needed. The DPJ already holds the upper house.

For the long-ruling Liberal Democratic Party (LDP) there was no disguising its anguish, as discredited heavyweight after heavyweight fell, often to young, telegenic DPJ novices shrewdly drafted in as giant-killers. Taro Aso, the visibly shaken prime minister, conceded defeat, describing the result as “very severe”. When he dissolved parliament in July to hold the elections, the LDP held 300 seats. NHK’s count showed it had won 119 seats so far, almost the same as the puny number the DPJ held before the elections.

The raw numbers, however dramatic, only partly tell of the upheaval this could mean for Japanese politics. The LDP has had its hands on almost every lever of power for more than half a century; even when it briefly lost office in 1993, it regained it within 11 months because the forces assembled against it fell apart.

During much of its tenure, it held power because it helped deliver rising prosperity to a country that had only recently endured the ignominy of second-world-war defeat and American occupation. After taking office in 1955, it turned Japan into one of America’s firmest cold-war allies.

But as Japan’s economic miracle faded, and the country sank into a deflationary funk in the 1990s, the LDP clung onto power largely thanks to an entrenched system of patronage and lavish use of the pork barrel. It used public funds or access to Japan’s vast pool of private savings to launch public-works projects that for its last two decades in power kept its grass-roots supporters, such as farmers and construction workers, loyal.

None of that spending generated a sustainable recovery, however, nor did reforms by Junichiro Koizumi, a political one-off who revived the LDP’s fortunes during the last election in 2005, but whose followers, known as “Koizumi’s children”, were crushed by the DPJ this time round. Instead Japan has become saddled with a debt projected to rise to twice the country’s ¥497 trillion ($5.3 trillion) GDP, and it remains dangerously dependent on its large exporters. Figures released in the closing days of the campaign showed unemployment, exacerbated by the global financial slump, hit a record 5.7% in July. Deflation has also re-emerged; consumer prices fell 2.2% in July from a year earlier.

The LDP’s failure to improve people’s lives was one of the twin pillars of the DPJ’s successful campaign. The other was the LDP’s complicity with an all-encompassing bureaucracy that has been guilty of staggering incompetence recently, not least by losing millions of personal-pension records in 2007. The public has also been vexed by the practice of rewarding top civil servants with plum jobs at firms they formerly supervised. The DPJ has vowed to stamp out that policy.

But how well it can fulfill its manifesto pledges—repeated with worthy insistence on the campaign trail—will depend on many factors. Firstly, it may need to reach some sort of accommodation with civil-service mandarins, because only a handful of its most senior members have experience at cabinet level. Its spending proposals are largely to be funded by cutting waste from government spending; that is always easier to promise than to deliver.

Meanwhile, Japan’s economy is still poised precariously between recovery and renewed slump. If the recovery fails to materialise, it will not necessarily be the DPJ’s fault. But it will be the first test of its administrative competence in a country that is crying out for good leadership.

Besides naming a cabinet, Mr Hatoyama, who has appeared to flip-flop on sensitive issues such as Japan’s occasionally subordinate relationship with America, is soon likely to have to step onto the world stage. He hopes to travel to New York in September for the UN general assembly, and will probably meet Barack Obama on that trip.

But as he sets out to introduce a new era of political openness and accountability to Japan, he will be dogged by a thorny question that was already being put to him as he cautiously claimed victory on Sunday night. That is the position of Ichiro Ozawa, the DPJ’s former leader, who orchestrated this remarkable election victory and is a master manipulator eminently capable of pulling Mr Hatoyama’s strings.

So far, the new leader has ducked the question. But Japan, for all that it will celebrate dealing the LDP a punishment it has long deserved, will want an answer. Otherwise its people may fear they have replaced one dark force with another.